Synthesis and Computational Study of an Optical Fluorescent Sensor for Selective Detection of Ni²⁺ Ions

The presence of an abnormal amount of Ni²⁺ in the human body causes various health issues. Therefore, this work aimed to synthesize the curcumin-based fluorescence-on sensor [2,6-bis((E)-4-chlorobenzylidene)-cyclohexan-1-one] that was capable of selectively responding to Ni²⁺ ions in aqueous solution. The structure of was confirmed by ¹H NMR and Fourier transform infrared (FTIR) spectroscopy. The Ni²⁺ ion sensing was based on the fluorescence enhancement of the fluorophore () in neutral aqueous medium. The response of the -based sensor was highly selective toward Ni²⁺ ions, whereas the possible interferences from other metal cations were negligible. had a fast response; it was selective and had a sensitive detection limit (LOD = 2 × 10^-10 M) toward Ni²⁺ ions in neutral medium with a high association constant (K) value of 3.6 × 10⁵ M^-2 for the complex formation between the and Ni²⁺ ions. Job's plot and DFT calculations proved that the binding stoichiometry of for Ni²⁺ was 2:1. was recovered using EDTA as a chelating agent after being employed as a fluorescent sensor. These characteristics ensured the potential use of as a new class of chemosensor for environmental applications.